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Re: Disk Drive Cloning - HPDL360 G5 SAS Drives

 
Rose Kucharczyk
New Member

Re: Disk Drive Cloning - HPDL360 G5 SAS Drives

We configured RAID 1 + hot spare. It is a configurable option within the RAID build.

These servers are slated to be Citrix servers in a large farm. We chose the RAID 1 + hot spare because the RAID 1 configuration allows for fault tolerance and cloning, which RAID 5 does not. The idea of a hot spare is that the RAID can be rebuilt and we can have a fully functioning server without having to wait for a drive replacement from HP. The cloning feature is almost a necessity when deploying 25+ servers with the same build.

Our company does not have a server imaging solution in place at this time, therefore we use RAID 1 in these types of builds to allow for the cloning without software.
Andrew_346
Regular Advisor

Re: Disk Drive Cloning - HPDL360 G5 SAS Drives

Rose,

I'm not sure what hardware you've done this RAID cloning with, but I think a guy I once worked with tried this with HP controllers and it never worked.

If memory serves me right, HP controllers will not import a failed array. If you take one of the drives in a mirror to another server and attempt to use that hard drive to boot the system, the controller will not let you. It will see it as only half of a healthy array and not import it the same way as if you took both drives to a new system.

Since you say that this is a rollout of 25+ servers, I would STRONGLY suggest you invest in some type of imaging software.

RDP is available for a 7-day trial with up to 10 nodes. Give it a shot. http://h18013.www1.hp.com/products/servers/management/rdp/index.html

If you don't like it, there are many others out there. Symantec Ghost, Acronis, etc.

Mauro Rusignuolo
Trusted Contributor

Re: Disk Drive Cloning - HPDL360 G5 SAS Drives

Coming back to your problem of the original post, I make a preliminary statement:

I haven't a direct experience on this server.

In order to try to answer to your question I can suppose that your 3 HDs are 40 GB each.

I explain why I suppose this.

The array you are talking about, may be is a RAID 1E.
incorrectly called, above, RAID 1 + Hot Spare.

the third HD (that is not Third), is not a really Hot Spare because doesn't add any fault tolerance to the RAID 1.

RAID 1, as known, is the mirror of one HD on another.
Is fault tolerant; the usable capacity is 50% of the total capacity.

RAID 1E, as said, doesn't add any fault tolerance. RAID 1E combine data stiping and data mirroring. Can be implemented, obviously, with an odd number of HDs.
Doesn't allow multiple drive failures.

Data is written simultaneously to two HDs (ever).

If you use 3 HDs of 40 GB, like said above,
you can use 60 GB of total capacity.

So, let's call the 3 HDs : 1A, 2B and 3C
the total data you can write splitting the 60GB total in 6, will be:
1d, 2d, 3d, 4d, 5d, 6d.

Now, data are stored or written in this way:

disk 1A:
1d
3d
4d
6d

disk 2B:
2d
1d
5d
4d

disk 3C:
3d
2d
6d
5d

You can see that no one contain the "full data" like in mirror.

The only advantage, compared with RAID 1, is in the "read operation".

So, it's explained because you cannot remove one HD from the hot-swap bay and insert the disk to another hoping in a boot.

This is right if the raid you implemented is a RAID 1E like explained.

I hope this should be useful.

Bye.

TJK

<> Leonardo da Vinci
Neal Bowman
Respected Contributor

Re: Disk Drive Cloning - HPDL360 G5 SAS Drives

Jackal,

Your explaination may be accurate for RAID controllers made by vendors other than HP.

For all Smart Array Controllers made in the last 10 years, a RAID1 array consists of 2 (or 4 or 6) hard drives. It has to be an even number. Data is written to all hard drives equally. Since all drives have the same info sprad across the array of 2 (or 4 or 6) drives, you can lose one of the drives, and the server remains functional. With the on-line spare, this is an additional drive that is available to pulled into service, should one of the drives in the array fail. Without an on-line spare, the array will function in a degraded status until the failed drive is removed from the array and replaced with a good drive. The array rebuilds that data from the good drive to the new drive, then all is running at 100% again.

The on-line spare reduces the amount of time the array is running in a degraded status by rebuilding the array as soon as the first drive fails. In effect, this is an insurance policy. You hope you never have to use it, but are glad you have it when it happens to you. This also adds an additional level of fault-tolerance in case the remaining good drive happens to fail before the failed drive has been replaced.

Rose,

As others have mentioned, you will not be able to migrate a single drive to clone a server. What you may want to test, is remove the online spare from the array, if you have one by using the Array Config Utility and save the configuration.
Remove disk0 and replace it with a new blank drive. Let it rebuild completely.
Place the removed drive in the new server. Do not power up the new server yet.
Remove disk1 from the original server, and replace with a new blank disk.
Let the array rebuild completely again. The time required for this will depend on the size of the hard drives and the amount of data on the drives.
Insert the second removed disk into the new server. Turn on the power and watch the POST messages. If it detects the proper number of logical drives, you MAY be in business.

As others have pointed out, you should look at a true imaging solution. Once you have created your source image, you can push it to new replacement servers in less amount of time than going through the process I have described. My process may take a couple of hours while you wait for arrays to rebuild, whereas you can push an image to a new server in 20-30 minutes each, if you do one at a time. Some imaging solutions allow you to multicast the image to multiple servers at once, all in the same 20-30 minute window.

Hope this helps,
Neal
Mauro Rusignuolo
Trusted Contributor

Re: Disk Drive Cloning - HPDL360 G5 SAS Drives

Hi Neal,

here, in Italy, it's very late night.
I'm no able to sleep.

Thinking again at what you have write ... I came back at the keyboard.

thank you of the axplaination.

let me say a sentence I've learned: "preliminary statement"... so:

PRELIMINARY STATEMENT - what I'm writing it's not regarding anyone personally but are general consideration.

I see that, sometimes, practice and theory doesn't follow the same direction.

The called "RAID 1 + hot spare" should be called "RAID 1 + waiting HD".
n theory, doesn't exist.
In the case mentioned above, the third HD hasn't any function in the RAID.
Before one HD faults, obviously.

ah ... HP Invent...
and, if I want to stay peaceful ... I can ask "HP invent" RAID 1 + 2 waiting HDs... and so on...
If I want to stay peaceful for a sabbatical year I can ask "HP invent" RAID 1 + 10 waiting HDs...

"HP invent" a new way to increase the number of unemployed people all over the world !

I can suggest, to the engineers and the project managers of HP (may be they have already INVENTed it :-)": "RAID 1 + autoloader over multiple machines" ... using HDs instead of cartridges...

Here, we usually say, in situation like this (referring to the ideas): Small in number - Big in dimension.

Ah ... HP Invent ...

good slogan.

good night to all.

Hi, Neal: thanks again for the explaination.

TJK
<> Leonardo da Vinci